"The followers of Plato generally adhered strictly to his psychological theories. Several, however, like Xenocrates, ventured into bolder speculations. Speusippus, the nephew and successor of the great philosopher, was the author of the Numerical Analysis, a treatise on the Pythagorean numbers. Some of his speculations are not found in the written Dialogues; but as he was a listener to the unwritten lectures of Plato, the judgment of Enfield is doubtless correct, that he did not differ from his master. He was evidently, though not named, the antagonist whom Aristotle criticised, when professing to cite the argument of Plato against the doctrine of Pythagoras, that all things were in themselves numbers, or rather, inseparable from the idea of numbers. He especially endeavored to show that the Platonic doctrine of ideas differed essentially from the Pythagorean, in that it presupposed numbers and magnitudes to exist apart from things. He also asserted that Plato taught that there could be no real knowledge, if the object of that knowledge was not carried beyond or above the sensible."